Spring wound mechanical intervalometer



June 11, 1957 L. KIELMAN 2,795,661

SPRING WOUND IECHANICAL INTERVALOIIETER Filed April 12. 1956 2 Sheets-Sheet 1 I2 22 58 1/ F- I 54 3,; 30 29 A6 4 I: 42 1 73 I, 66

I ,1! J i 5| J II I INVENTOR. LEO L. KlELMAN BY I I ATTORNEYS June 11, 1957 L. L. KIELMA SPRING ROUND MECHANICAL INTERVALOIIETER Filed April 12. 1956 2 Sheets-Sheet 2 INVENTOR. LEO L. KIELMAN BY M@@ w ATTORNEYS United States Patent SPRING WOUND MECHANICAL INTER- VALOMETER Leo L. Kielman, China Lake, Calif., assignor to the United States of America as represented by the Secretary of the Navy Application April 12, 1956, Serial No. 577,901

3 Claims. (Cl. 20028) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to electrical switches and particularly to a mechanically operated intervalometer.

Heretofore, cascade resistance type and motor driven commutator type intervalometers have been used. The cascade resistance type intervalometer usually comprised a series of contacts, each contact being placed on a long strip of narrow, but thin metal. Each metal strip was fastened rigidly at one end, while the contact bearing end of each strip was held off its mating contact by means of a small resistance wire. Current was made to flow through the resistance wire, which in a short interval of time caused the wire to part and allowed the strip contact to close the circuit with its lower contact. The procedure also allowed the current to flow to the next strip contact and 1 thus repeated itself in parting the resistance wire and closment of the resistance wire. Likewise, the disadvantage of the cascade resistance type intervalometer is that it is expensive and requires external power to drive the unit.

The present invention avoids the disadvantages associated with these prior type intervalometers by providing a spring wound mechanically operated intervalometer which has no delicate adjustments, and is relatively small and inexpensive.

in accordance with the foregoing, it is an object of the present invention to provide an intervalometer in which the time intervals may be varied easily, and which contains a self-powered drive mechanism.

Another object of the invention is to provide a mechanically operated spring wound intervalometer in which only one circuit is closed at any one time.

A further object of the invention is to provide a mechanical intervalometer that is relatively small and inexpensive.

Other objects and many of the attendant advantages of the present invention will become apparent as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a cross-sectional view taken along the axis of the intervalometer;

Fig. 2 is a plan view of a segmental contact assembly;

Fig. 3 is a perspective view of the intervalometer of the present invention.

Referring to the drawings where like numbers refer to like parts throughout all the figures, the construction of the spring wound mechanical intervalometer of the present invention is as follows: A wafer section switch or Patented June 11, 1957 "ice segmental contact assembly 10 is used since this type of switch possesses all the desired features which are desirable in the switching mechanism. Two spaced bearing plates, 12 and 14, are mounted on support member 16 by means of two long machine screws 18 and 20. Spacers 22 and 24, through which pass machine screws 18 and 20, are used to keep bearing plates 12 and 14 spaced a desired amount. Wafer section switch 10 is mounted on the ends of machine screws 18 and 20 with nuts 26 and 28, for example. Spacers 30 and 32 keep wafer section switch 10 at a desired spacing from bearing plate 12. Switch drive shaft 34 has one end 35 which is flattened so as to be accommodated in slot 36 in the segmental contact assembly 10. Drive shaft 34 passes through stand off bearings 37 and 39 each mounted in a hole in the center of bearing plates 12 and 14, respectively; shaft 34 also extends through a hole in support member 16. The center portion of drive shaft 34 is provided with a slot at 38 which is used to anchor one end of a clock spring 40 to the shaft. Clock spring 40 is installed and aligned between the two bearing plates 12 and 14. One end of clock spring 40 is formed to fit the anchorage slot at 38 on the shaft, while the other end is formed into a loop 42 which is anchored around machine screw 22.

The speed governor control 44 is on the opposite end of drive shaft 34 from wafer section switch 10. Speed governor control 44 is comprised of two metal discs 46 and 48 which are used as fly weights and which are mounted on a short shaft 50 that straddles the main drive shaft 34. Short shaft 50 has an enlarged center portion 51 which is bored to be accommodated by and fastened to the end of drive shaft 34. Light coiled springs 54 and 56 are placed over each end of shaft 50 behind the metal discs 46 and 48. Springs 54 and 56 are held in place by washers 58 and 60, which are made from strong but lightweight material such as fiber. Washers 58 and 60 are in turn held in place by small machine screws 62 and 64 which are threaded into the ends of short shaft 50.

A small ratchet device is used to provide a means for releasing the mechanism when it is in a wound-up state. The ratchet device consists of a small pinion gear 66 fastened to the drive shaft 34, and a pawl spring arrangement 68 mounted on support 16 for holding or releasing pinion gear 66.

Wafer section switch 10 is comprised of a base 70 made from an insulating material having good mechanical strength, such as a micarta material on which segmental terminals 72 and contact terminal 73 are mounted. Base 70 is also provided with a shorting contact plate 74 and segmental contact 76 which contact the segmental terminals 72. Base 70, bearing plates 12 and 14, and support 16 together comprise the intervalometer support member which supports the contacts and terminals, drive shaft and bearings, and speed regulating governor. Wafer section switch base 70 includes a separate central movable portion 75 on which segment-a1 contact 76 is mounted. Shorting contact plate 74 is also mounted on portion 75 which rotates with drive shaft 34. Segmental contact 7 6 is electrically connected to segmental contact terminal 77 through rivet 78 and base plate 79.

The spring wound mechanical intervalometer is operated as follows: The clock spring 40 is wound up and the pawl 68 set to hold it in this position. At the time the pawl release 68 is actuated the discs 46 and 48 of governor control 44 are bearing against drive shaft 34 and the mass concentration is localized about the center of the drive shaft. This condition allows the drive mechanism to get ofi to a fast start. As the rotating effort continues there is a tendency for the drive to accelerate. This accleration causes the fly weight discs 46 and 48 to travel outwardly along shaft 50 and distribute the mass of the metal discs farther away from the drive shaft center.

The tendency then, is for the mechanism to decelerate and thus hold the rotative speed constant. "In general, the action of the governor is to control the speed of the device.

When the drive shaft is in motion, it drives the segmental contact 76, which in turn makes contact with the individual contact terminals 72 around the circumference of the wafer section switch 10. As the segmental contact 76 engages the terminals 72 progressively around the wafer 70, the circuit is completed to the external mechanism (not illustrated) and the function of the switching mechanism is realized.

With the. device of the present invention only one circuit is closed at any one time, while all the other circuits are short circuited. The time intervals of "the present intervalometer may be easily varied bysimply changing the tension of springs 54 and 56 .on governor 44.

The metal fly weight discs 46 and 48' may be made to conform to the contour of drive shaft 34, allowing them to seat about the drive shaft center. Also, theuse ofbearings 37 and 39 made from a suitable graphitic substance would dispose of the problem of lubrication as well as minimize bearing friction.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An intervalometer comprising a support member, a drive shaft rotatable in said support member, spring means for driving said shaft in rotation, a series of individual angularly spaced contacts carried by said support and disposed on a circle having the axis of shaft rotation as its center, a segmental contact carried by said shaft and,

adapted to sequentially engage said individual contacts upon rotation of said shaft, governor means on said shaft for controlling the speed of shaft rotation, a holding pinion mounted on said drive shaft and a pinionrelease means mounted on said support member for preventing said shaft from rotating until released.

2. An intervalometer comprising a support member, a

support member, spring means for driving said shaft in rotation, a series of individual angularly spaced contacts carried by said support and disposed on a circle having the axis of shaft rotation as its center, a segmental contact carried by said shaft and adapted to sequentially engage said individual contacts upon rotation of said shaft and close only one circuit at any onetime, a terminal in electrical contact with said segmental contact, a shorting contact plate for electrically shorting out all other circuits but said one circuit, a terminal in electrical contact with said shorting plate, and governor means on said shaft for controlling the speed of shaft rotation.

3. An intervalometer comprising asupport member, a drive shaft mounted in bearings and rotatable in said support member, spring meansfor, driving .said, shaft in rotation, a series of individual angularly spaced contacts carried by said support and disposed on a circle having the axis of shaft rotation as its center, a segmental contact carried by said shaft and adapted to sequentially engage said individual contacts upon rotation of said shaft and close only one circuit at any one time, a terminal in electrical contact with said segmental contact, a shorting contact plate for electrically shortingout all other circuits but said one circuit, a terminal in electrical contact with said shorting plate, a holding pinion mounted on said drive shaft and a pinion release means mounted on said support member for preventing said shaft from rotating until released, said spring means having one end fastened to said drive shaft and its other end fastened to said support member, and a governor means on said drive shaft for controlling the speed of shaft rotation.

References Cited in the file of this patent UNITED STATES PATENTS 1,007,177 :Bevans Oct. 31, 1911 2,186,949 Allison et al. Jan. 16, 1940 2,388,686 Habig Nov. 13, 1945 2,665,343 Benson Jan. 5, 1954 2,750,459 Hosea et al. June 12, 1956 

